The present invention generally relates to electrostatic precipitators that aid the efficient collection and elimination of dust and mist from industrial effluent gases, and more particularly to an improved traveling spray assembly for washing of the internal components of electrostatic precipitators.
The efficient collection and removal of the many and various dusts and mists that are found in industrial gases has been the goal of and is the basis for continued improvements in the electrostatic precipitator field. The conventional electrostatic precipitator for industrial particulate control has utilized an electrical corona generated between two electrodes for the electrical charging of dusts and mists that are suspended in the gaseous stream that is flowed between the electrodes. Such conventional electrostatic precipitators are known as "single-stage" electrostatic precipitators. Electrostatic precipitators in U.S. Pat. Nos. 4,056,372 and 4,381,927 are referred to in the field as parallel-plate, two-stage type electrostatic precipitators. Such electrostatic precipitators employ sets of plates that are divided further into two sub-sets of plates such that every other plate belongs to the same sub-set. Each sub-set is maintained at a different electrical potential by a direct current source. Additional developments in electrostatic precipitators of the parallel-plate type can be found in U.S. Pat. Nos. 4,381,927 and 4,342,571.
Another class of two-stage electrostatic precipitators are the grid-type which employ conventional ionizers in combination with perforated plate collectors. The construction of grid-type electrostatic precipitators calls for the perforated plates to be positioned perpendicular to the gaseous stream so the particles are deposited on the grids as the gas stream flows therethrough. Alternatively, a portion of the gases can be extracted through a permeable electrode to improve deposition as proposed in U.S. Pat. No. 4,481,017.
Regardless of the type of electrostatic precipitator and its mode of operation, the collector plate electrodes lose their efficiency for collection of additional particulate matter upon build-up of the particulate matter thereon. Accordingly, the electrostatic precipitator, or in most cases only the fouled field of collector plate electrodes, must be pulled off-line periodically for the collector plate electrodes to be cleansed of the collected particulate matter. The plate electrodes can be vibrated, subjected to sonic disruption, flushed with washing fluid, or subjected to additional techniques for removal of the collected particulate matter and re-establishment of the collector plate efficiency. Washing of collector plate electrodes can be accomplished by a stationary spray header pipe as shown in U.S. Pat. No. 2,608,266, or can take the form of a traveling vertical header mounted on a pair of tracks and connected to a flexible hose and which is moved by a drive cable along the extent of a bank of upstanding parallel, spaced-apart collector electrodes. Such traveling header spray systems have been marketed for several years commercially. Such systems are limited in the length of the bank of collector plates that can be washed by the length of the flexible hose connected to the vertical spray header pipe. Also, the washing fluid is sprayed from one end of the collector plates only which makes cleaning of the areas of the collector plate disposed opposite the spray header difficult. Thus, there is a need in the art for improved traveling spray assemblies adapted for washing of vertically-mounted, spaced-apart collector plate electrodes disposed in electrostatic precipitators.